I have carbs for either alky or gas. Will probably try both.
For a start it will be going in 3500lbs panelvan, for 1/8th mile racing, but later probably end up in street car.
have TH400, with 9" convertor that I'll send in to get rebuilt to suit final combo. 4.56 diff, 10.5x28 slicks.
Also have 150hp nitrous to be fitted later.

Any advice, or comments appreciated, plus any guess's at HP. I was hoping for 600-650hp N/A.

My other question is about blocks.

I was looking at Dart little M,
But have then seen Dart SHP blocks, which I can get for aprox$1000 cheaper, altho looking at Darts site, they say they are good for 600HP. Has anybody got any good or bad stories about them, and would the SHP block be strong enuff for my combo?
Or would I be better off still going for the little M block?

Are Dart blocks better than chev Bowtie blocks?
If so, why? and what shortfalls do either have?

The SHP block will be a much better foundation to build from Vs a stock production 400 block.

Let me throw this on the table. If you don't think you will ever build a larger or more powerful small block, then the SHP will fulfill your requirements nicely. However, if you do think you might want to step up down the road, I would suggest looking at another block that will allow you room to grow and you need only to buy one block. That is Dart's Iron Eagle block.

They also are showing $1750.00 for a billet main Little M 400 block. Holy crap!! they want $1525 for an SHP!! Guess they are going off their sales volume for their discount.

I have one of these coming from Cobra on Tuesday. It is being shipped direct from Dart. $1750 shipped, got $32 ebay bucks, so actually $1718 shipped. Bought it with Paypal, so I dont even have to pay for it till the card turns over.
Their ebay ad says they have two more to sell. Why buy a lesser block?